As the electronics industry progresses integrated circuit (IC) products are shrinking in size. The applications supported by these IC's are becoming more powerful with ever increasing features and functions. This is exemplified as the telephone was transformed into the cellular phone and most recently into the camera phone. All the while these devices continue to shrink in size. Other devices that have evolved include computers, memory devices, personal music players and personal data assistants (PDA's). Each is operated by an integrated circuit die.
An IC die is a small device formed on a semiconductor wafer, such as a silicon wafer. A leadframe is a metal frame that usually includes a paddle that supports an IC die that has been cut from the wafer. The leadframe has lead fingers that provide external electrical connections. That is, the die is attached to the die paddle and then bonding pads of the die are connected to the lead fingers via wire bonding or flip chip bumping to provide the external electrical connections. Encapsulating the die and wire bonds or flip chip bump with a protective material forms a package. Depending on the package type, the external electrical connections may be used as-is, such as in a Thin Small Outline Package (TSOP), or further processed, such as by attaching spherical solder balls for a Ball Grid Array (BGA). These terminal points allow the die to be electrically connected with other circuits, such as on a printed circuit board.
Use of packaged ICs is widespread. Moreover, the size and cost of electronic devices puts continuous pressure on the need for small, yet less costly packaged ICs. Furthermore, for high bandwidth RF devices and high operating frequency devices, there is a push for shorter electrical paths inside the IC package. Flip chip bonding can replace the traditional wire bonding interconnection.
There are also manufacturing issues that plague the flipchip assembly process. With the attachment of the flipchip solder balls to the leadframe or substrate, the IC die has a tendency to move during the reflow connection. As the solder becomes viscous, the die can be moved by the surface tension in the liquid solder. Due to the small size of the IC die, it is difficult to hold the IC die in a fixed position. Any movement during the attachment process can cause a package failure and reduced yield.
A key component in the die attach process is the leadframe preparation. As the solder liquefies, during reflow, it will flow to any surface that will bond with it. Preparing a leadframe for flipchip attachment can be a meticulous and costly process. Thus, it is desirable to provide an inexpensive method of flip chip interconnection packaging ICs. It also is desirable to have a method of decreasing the size of such packaged ICs.
Thus, a need still remains for a reliable high volume capable process for flipchip assembly on leadframe packages. In view of the demand for high volume low profile packages, it is increasingly critical that answers be found to these problems. The ever increasing need to save costs and improve efficiencies, makes it is more and more critical that answers be found to these problems. Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.